Osteoarthritis (OA) is by far the most prevalent joint disorder today. The knee and the hip are large joints to be targeted and is an important cause of pain and disability. In knee OA, it is shown that significant risk factors in developing the disease are quadriceps weakness, joint instability, and changes in joint loading. A few studies on hip OA have shown altered gait pattern, which affect joint loading, and one study has shown weakness in abductors, adductors and flexors around the hip. As joint loading and muscle weakness are important factors in the development in knee OA, it might as well be factors influencing OA in the hip. The purpose of this case-control studies was to compare hip OA patients to a healthy control group regarding biomechanical and clinical differences. Patients with hip pain, activity limitations (Harris Hip Score 60-95 p) and radiographically verified hip OA was included. The healthy control group will have a Harris Hip Score of 100 p. One hundred and ten patients and fifty controls will be asked to fill in questionnaires on pain, stiffness and physical function (WOMAC), quality-of-life (SF-36 v2), self-efficacy (Lorigue), and activity (PASE) in addition to perform 6-minute walk test, sub-maximal cardiovascular function, strength, and hip range of motion tests. Additionally, Qualisys Pro reflex 3D motion analysis system will be used during walking, one-leg standing, and raising from a chair on a sub-group of 40 patients and 20 controls.